The cooling system on the 3.0L is not logical by any means and I made that flowchart after several cold starts and the scientific thoroughness of a hand on each hose.......................

Some aspect are without doubt and one is that hot water flows into the top hose and top radiator neck. The thermostat is remote and until it opens, there's a return flow through the narrow pipe from the filler neck into the header tank, with lots of turbulence.

The flow from the water pump to the heat exchanger, then to the header tank could be the opposite way, but that's not how it feels!!

When the thermostat opens, and this takes a long time, the flow is from the bottom hose at the radiator.........

On a cold morning, it takes ages to get the thermostat to open. It can be detected by a twitch on the temp gauge.

The 3.7L will not be like this!!!

DaveW
'05 Red Roadster S1
'16 Yellow (Not the only) Narrow AR GDI Plus 4